Abstract

We prove large deviations principles (LDPs) for the perimeter and the area of the convex hull of a planar random walk with finite Laplace transform of its increments.

Highlights

  • Let (Sk)k 1, where Sk = X1 + . . . + Xk, be a planar random walk with independent identically distributed increments X1, X2, . . . We assume that the expectation of X1 exists and is finite, and put μ := EX1

  • Abstract. — We prove large deviations principles (LDPs) for the perimeter and the area of the convex hull of a planar random walk with finite Laplace transform of its increments

  • For random walks with such increments, large deviations of the perimeter are attained by the trajectories that asymptotically align into line segments

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Summary

Introduction

We found the rate function for random walks that have rotationally invariant distributions of increments with finite Laplace transform (Theorem 2.11) and for Gaussian random walks with arbitrary drift (Theorem 2.13 and Proposition 2.15) In all these results we identified the asymptotic form of optimal trajectories of the walk resulting in the large deviations. We extended the above results on random walks, which have increments in discrete time, to convex hulls of planar Lévy processes (Theorem 2.16) with finite Laplace transform, including Brownian motions.

Notation
Large deviations of the perimeter
Large deviations of the area
Convex hulls of Lévy processes
Higher dimensions
Weaker exponential moments assumptions
Basic facts from convex analysis
Basic properties of the radial minimum function I
Radial maxima and minima of conjugate convex functions
Convexity of the radial minimum function I
Basic facts on large deviations
Main proofs
The LDP’s in continuous time
The LDP’s under the Cramér moment assumption
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